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Purpose: o The purpose of my experiment was to determine which type of toothpaste would whiten teeth the best that were severely stained by coffee.

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Hypothesis: o My hypothesis was that out of all of my four toothpastes (Crest Lemon Whitening Expressions, Arm & Hammer Extra Whitening, Colgate with Whitening, and Pepsodent Triple Whitening) I thought that Arm & Hammer Extra Whitening was going to be the best whitener. Why you ask did I think this would be the best? Even though I dont use this toothpaste, my Dad used to, and he drinks alot of coffee. I saw a dramatic change with his teeth after using this toothpaste.

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Method: The steps of doing my experiment were: 1. First I boiled 4 eggs in very strong coffee for a period of 15 minutes. 2. After that, I rinsed them off under cold running water and left them for 24 hours to make sure the stain would set. 3. The next day, I brushed all 4 eggs for one minute each with a different brand of toothpaste and recorded which one was whitest. 4. That night, I brushed all 4 eggs again for one minute each and recorded my results again. 5. I Repeated Steps 3 and 4 everyday for one week.

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Variables: My variables for this experiment were: o My manipulated variable was the toothpaste, for every egg I had a different brand of toothpaste. o My controlled variables were the brushing time for each egg I brushed them for one minute exactly and the size of the spot that I was brushing to determine the whitening. o My responding variable was determined by my manipulated and controlled variables. Due to these variables, my responding variable was which egg whitened the best and in my experiment the Crest Lemon Whitening Expressions made the biggest change in whitening.

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Conclusion: With my experiment I determined which toothpaste would whiten teeth the best that were severely stained by coffee. In my hypothesis within my 4 brands of toothpaste (Crest Lemon Whitening Expressions, Arm & Hammer Extra Whitening, Colgate with Whitening, and Pepsodent Triple Whitening) I thought that Arm & Hammer Extra Whitening would whiten the eggs best. But I was wrong, and Crest Lemon Whitening Expressions whitened the best, second was a tie between Pepsodent Triple Whitening and Colgate with Whitening and last but not least my prediction Arm & Hammer Extra Whitening.

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Sources of Error: Some sources of error that occurred in my experiment were that I used different amounts of toothpaste, I could of brushed with more strength on some eggs then I did on others and some coffee stains on the eggs were darker than others. All these had an effect on my results.

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Ways to Improve: Just like I said in Sources of Error that I used different amounts of toothpaste, I could of brushed with more strength on some eggs then I did on others and some coffee stains on eggs were darker then others. If I were to do this project again I would of measured how much toothpaste I put on the toothbrush for each egg, I would of tried to brush with the same strength every time and I would of made sure that the coffee stains were all similar to each other. If I improved all this, my experiment would be more sufficient then ever before.